//===--- BCReadingExtras.h - Useful helpers for bitcode reading -*- C++ -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

#ifndef POLARPHP_SERIALIZATION_INTERNAL_BCREADINGEXTRAS_H
#define POLARPHP_SERIALIZATION_INTERNAL_BCREADINGEXTRAS_H

#include "llvm/Bitstream/BitstreamReader.h"

namespace polar::serialization {

/// Saves and restores a BitstreamCursor's bit offset in its stream.
class BCOffsetRAII {
   llvm::BitstreamCursor *Cursor;
   decltype(Cursor->GetCurrentBitNo()) Offset;

public:
   explicit BCOffsetRAII(llvm::BitstreamCursor &cursor)
      : Cursor(&cursor), Offset(cursor.GetCurrentBitNo()) {}

   void reset() {
      if (Cursor)
         Offset = Cursor->GetCurrentBitNo();
   }

   void cancel() {
      Cursor = nullptr;
   }

   ~BCOffsetRAII() {
      if (Cursor)
         cantFail(Cursor->JumpToBit(Offset),
                  "BCOffsetRAII must be able to go back");
   }
};

} // end namespace polar::serialization

static constexpr const auto AF_DontPopBlockAtEnd =
   llvm::BitstreamCursor::AF_DontPopBlockAtEnd;

#endif // POLARPHP_SERIALIZATION_INTERNAL_BCREADINGEXTRAS_H
